Variable resistance



M. PODELE VARIABLE RESISTANCE Nov. 30 1926. 4 I 1,609,191

Filed Dec. 5. 1923 I Witnzs5 es Inventor cury, and the=extension 8. 'Thus'the effective length of the coating 7 in circuit can be varied, and the resistance of the device can be adjusted to be greater or smaller, according to the relative posit-ionsof the mercury and the casing, as desired.

Any suitable high resistance material can be used besides india ink and other substances besides mercury maybe employed if desired, provided .the materials for the coating and ,the liquid constituting the element 10 are .240 selected that they do not affect one another chemically, and are otherwise satisfactory for my purpose.

'Havingdescribed :my invention, What I .be- .lieve to be new anddesire to secure and protect by .Letters Patent of the United (States to rotate about its central axis in horizontal position, the inner surface of said casing having a conductive coating, and the inner surface of said casing also having a curved resistance coating thereon spaced from said conductive coating, and a freely movable quantity *of z'flu'id conductive substance in said casing to connect the two coatings and vary-the portion of the length of the curved coating in circuit with saidv substance, .to .ad j ust the valuerof said resistance, according to the relative positions of said substance and said curved coating.

2. The adjustable grid leak adapted for use in radio apparatus comprising a sealed multiple part insulating casing, .contacts projecting from :said casing to rotatably mount the same, resistancematerialarranged on :the inside ofsaid casing :adjacent the periphery thereof, and a movable connector insaid casing :and making contact With said resistance material to control the resistance in circuit between said contacts.

8. The adjustable grid leak adapted :for use in :radio apparatus comprising a casing, thin resistance .materialadhesively securedin position inside of said casing, and a relative l-y movable :liquid connector in said casing and making contact With said resistance material to control the amount of resistance in circuit.

MURRAY PO-DELL.

Patented Nov. 30, 1926.

UNITED STATES MURRAY PODELL, OF

PATENT OFFICE,

MOUNT VERNON, NEW YORK, ASSIGNOR OF ONE-HALF TO IIIAX C. KUPFER, OF BROOKLYN, NEW YORK.

VARIABLE RESISTANCE.

Application filed December 5, 1923.

This invention relates to improvements in variable resistances; especially variable or adjustable resistances of the kind known as grid leaks used in radio apparatus.

An object of this invention is to provlde an adjustable or variable resistance which is exceedingly simple, durable and efliclent, designed to operate with a minimum of friction between its fixed and the movable conductive parts, and capable of maintaining its accuracy under practical conditions.

The nature of the invention will be apparent from the following description and draw ings which disclose a preferred construction in which the invention is embodied, and I reserve the right to make changes in the details of structure and operation which come within the scope and spirit of the invention as the appended claims define same.

On the drawings,

Figure 1 is a front view of a case used in the practice of my invention with the cover removed;

Figure 2 is a section on the line AA of Figure 1;

Figure 3 is a face View of the cover for the case' Figure 4 is a section on the line BB of Figure 3; and

Figure 5 is an outside view of the complete device.

On the drawings, the same numerals iden tify the same parts throughout.

In the particular description of what the drawings present, I employ the numeral 1 to indicate the body of a cylindrical casing, the entire inner surface of the bottom of which is provided with an electrically conductive coating 2. This coating is made of some substance of high resistance such as india ink. The opposite end or top of the casing is open, but arranged to be closed by a cover or disk 4 which fits against the shoulder 5 and can be held in position by any suitable means. Both the bottom of the body 1 of the casing and the disk 4 are provided with projecting trunnions 6, which serve as journals, so that the casing can be mounted in bearings and revolve on these trunnions. As shown, the casing is cylindrical, and the central axis thereof will pass through the trunnions 6 which are in line with each other and when the casing is used, it will be mounted so that this axis is in horizontal position with the bottom of the body 1 and Serial No. 678,676.

the cover 4 vertical. The inner face of the cover 4 has a somewhat elongated circular coating 7, also of some material of high electrical resistance, such as india ink, one end of this coating being connected by an extension of the same material 8, to the center of the disk, and the other end being free, as indicated at 9. The body of the casing and the cover, except for the conductors 2 and 7, with the extension 8, will be of some insulating material, while the trunnions 6 will be, of conductive material. Hence, if the coating 2 is connected to the trunnion in the bottom of the body l,'as by making the inner end of this trunnion flush with the bottom so that it can come into contact with the coating 2, and if the extension 8 of the coating 7 makes contact with the other trunnion 6 of the disk 4, then, if conductors are placed in circuit with the trunnions 6, and the coatings 2 and 7 are bridged in thecasing, current in the circuit can flow through the casing from one coating to the other, provided some means is present in the casing to bridge the space between the coatings 2 and 7 For this purpose, I enclose in the casing a conductive element such as a drop of conductive liquid, such as mercury, which is metallic and liquid at ordinary temperatures, and will serve very well to connect the one coating to the other. This mercury on account of its fluidity and its weight is mounted to be free for bodily displacement relative to the easing and will always run down the inside cylindrical surface of the casing to the lowermost point; and current flowing between the two trunnions 6 will pass from the coating 2 to the mercury, to the coating 7, and by way of the coating 7 through the radial extension 8 to the trunnion of the disk 4; or in the as opposite direction according to which trunnion is connected to be electrically positive.

Therefore, if the case with the disk 4 be in such position that the end 9 of the coating is lowermost and the end 9 of the coating 7 10 is the only portion of this coating touched by the mercury, the current must flow through practically the whole length of the coating 7 before it can pass out by way of the trunnion mounted in the disk 4, and if the 105 casing be turned on the trunnions, the mercury will always run down to the lowermost point in the circumference of the casing, so

as to leave a shorter and shorter portion of the length of this coating between the mer- 110 

